Interbody spacer

ABSTRACT

An interbody spacer is provided including a body portion, first orifices, and second orifices. The body portion includes a distal end portion, a proximal end portion, first and second side surfaces that extend between the distal and proximal end portions, and top and bottom surfaces configured and adapted to engage vertebral bodies. The body portion includes a cavity defined through the first side surface and the cavity increases in volume at an interior portion of the body portion. The first orifices are defined through the top surface and the second orifices are defined through the bottom surface. One of the first orifices has a cross-sectional configuration different from that of one of the second orifices. A method of use therefor is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to, and the benefit of, U.S. Provisional Patent Application Ser. No. 62/108,197, filed on Jan. 27, 2015 and U.S. Provisional Patent Application Ser. No. 62/196,371, filed on Jul. 24, 2015. The entire contents of each of these prior applications are hereby incorporated by reference herein.

BACKGROUND

Technical Field

The present disclosure relates to an apparatus for treating spinal conditions, and more particularly, to an interbody spacer and a method of use therefor.

Background of Related Art

The human spinal column is a highly complex structure. It includes twenty-four discrete bones, known as vertebrae, coupled sequentially to one another to house and protect critical elements of the nervous system. The vertebrae interlock with one another to form a spinal column. Each vertebra has a cylindrical bony body (vertebral body), two pedicles extending from the vertebral body, a lamina extending from the pedicles, two wing-like projections extending from the pedicles, a spinous process extending from the lamina, a pars interarticularis, two superior facets extending from the pedicles, and two inferior facets extending from the lamina.

The vertebrae are separated and cushioned by thin pads of tough, resilient fiber known as inter-vertebral discs. Inter-vertebral discs provide flexibility to the spine and act as shock absorbers during activity. A small opening (foramen) located between each vertebra allows passage of nerves. When the vertebrae are properly aligned, the nerves pass through without a problem. However, when the vertebrae are misaligned or a constriction is formed in the spinal canal, the nerves get compressed and may cause back pain, leg pain, or other neurological disorders.

For many reasons, such as aging and trauma, the intervertebral discs can begin to deteriorate and weaken, potentially resulting in chronic pain, degenerative disc disease, or even tearing of the disc. Ultimately, the disc may deteriorate or weaken to the point of tearing and herniation, in which the inner portions of the disc protrude through the tear. A herniated disc may press against, or pinch, the spinal nerves, thereby causing radiating pain, numbness, tingling, and/or diminished strength or range of motion.

Many treatments are available to remedy these conditions, including surgical procedures in which one or more damaged intervertebral discs are removed and replaced with a prosthetic. After a partial or complete discectomy, the normally occupied space between adjacent vertebral bodies is subject to collapse and/or misalignment due to the absence of all or part of the intervertebral disc. In such situations, the physician may insert one or more prosthetic spacers between the affected vertebrae to maintain normal disc spacing and/or the normal amount of lordosis in the affected region.

Typically, a prosthetic implant is inserted between the adjacent vertebrae and may include pathways that permit bone growth between the adjacent vertebrae until they are fused together. However, there exists a possibility that conventional prosthetic implants may be dislodged and moved from their desired implantation location due to movement by the patient before sufficient bone growth has occurred.

Bone growth is a key factor in ensuring adequate retention of the implant to the vertebra. Specifically, bone ingrowth within and around the prosthetic implant promotes fusion between the adjacent vertebra, thereby strengthening the joint therebetween. However, conventional implants do not allow optimal space for bone ingrowth. In these instances, as the prosthetic implants do not mimic bone density of the adjacent vertebra, the body rejects the implant, and non-union (i.e., no fusion) occurs.

Conventional prosthetic implants are typically constructed in a manner that inhibits bone ingrowth, particularly those that include no spaces or avenues for such bone growth to occur within and around the prosthetic implant. The lack of fusion may allow the implant to become dislodged or moved from its desired location. Additionally, in the instances where the prosthetic implant includes a lumen for the packing of ingrowth material, the material is often able to dislodge from the lumen, and in some instances, from the implant, thereby reducing the chances that adequate bone ingrowth occurs.

Therefore, a need exists for a prosthetic implant that can mimic the density of bone or adequately retain ingrowth material therein to allow for optimal bone ingrowth and provide a solid fusion of the vertebral segments.

SUMMARY

In accordance with an embodiment of the present disclosure, there is provided an interbody spacer including a body portion having a distal end portion, a proximal end portion, first and second side surfaces that extend between the distal and proximal end portions, and top and bottom surfaces configured and adapted to engage vertebral bodies. The body portion includes a cavity defined through the first side surface and the cavity increases in volume at an interior portion of the body portion. First orifices are defined through the top surface and second orifices are defined through the bottom surface. One of the first orifices has a cross-sectional configuration different form that of one of the second orifices.

In embodiments, the cavity may include undercuts defined therein. An interior dimension of the cavity may increase in a direction towards each respective top and bottom surface. The cavity may include a greek cross cross-sectional configuration.

In embodiments, each of the first and second side surfaces may include an arcuate configuration. The body portion may define a kidney shaped configuration.

In embodiments, one of the first orifices may be offset from one of the second orifices. One of the first orifices may include a circular cross-section. One of the second orifices may include a diamond-shaped cross-section. One of the first orifices may include a circular cross-section and one of the second orifices may include a diamond-shaped cross-section.

In embodiments, the interbody spacer may be formed using an additive manufacturing process.

In embodiments, a portal may be defined through the second side surface. A threaded aperture may be defined through the proximal end portion. The threaded aperture is configured to threadably engage an insertion tool.

In embodiments, a plurality of ridges may be disposed on each of the top and bottom surfaces. Longitudinal grooves may be defined through each plurality of ridges.

In accordance with another embodiment, a method of performing spinal surgery is provided. The method includes preparing an intervertebral space between first and second vertebral bodies and advancing an interbody spacer into the intervertebral space. The interbody spacer includes a body portion having a distal end portion, a proximal end portion, first and second side surfaces that extend between the distal and proximal end portions, and top and bottom surfaces configured and adapted to engage vertebral bodies. The body portion includes a cavity defined through the first side surface and the cavity increases in volume at an interior portion of the body portion. First orifices are defined through the top surface and second orifices are defined through the bottom surface. One of the first orifices has a cross-sectional configuration different form that of one of the second orifices.

In embodiments, advancing the interbody spacer may include the interbody spacer having a cavity that includes undercuts defined therein.

In embodiments, the method may include packing the cavity with bone in-growth material. The method may include packing the cavity with drugs.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the present disclosure are described hereinbelow with reference to the drawings, wherein:

FIG. 1 is rear, perspective view, of an interbody spacer provided in accordance with the present disclosure;

FIG. 2 is a top, plan view, of the interbody spacer of FIG. 1;

FIG. 3 is a side, elevation view, of the interbody spacer of FIG. 1;

FIG. 4 is a rear view of the interbody spacer of FIG. 1;

FIG. 5 is a cross-sectional view of the interbody spacer of FIG. 1, taken along section line 5-5 of FIG. 3; and

FIG. 6 is a cross-sectional view of the interbody spacer of FIG. 1, illustrating an orifice defined through a top surface being offset from an orifice defined through a bottom surface.

DETAILED DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure are now described in detail with reference to the drawings in which like reference numerals designate identical or corresponding elements in each of the several views. As commonly known, the term “clinician” refers to a doctor, a nurse, or any other care provider and may include support personnel. Additionally, the term “proximal” refers to the portion of the device or component thereof that is closer to the clinician and the term “distal” refers to the portion of the device or component thereof that is farther from the clinician. In addition, for the purposes of this application, the term “lateral” indicates a direction toward a side of the body of the patient, i.e., away from the middle of the body of the patient. The term “posterior” indicates a direction toward the patient's back, and the term “anterior” indicates a direction toward the patient's front. Additionally, in the drawings and in the description that follows, terms such as front, rear, upper, lower, top, bottom, and similar directional terms are used simply for convenience of description and are not intended to limit the disclosure. In the following description, well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail.

Referring now to the drawings, FIGS. 1-5 illustrate one embodiment of an interbody spacer provided in accordance with the present disclosure generally identified by reference numeral 100. Interbody spacer 100 includes a body portion 102 illustrated as having a generally arcuate, kidney shape (FIG. 2); however, it is contemplated that body portion 102 may include any suitable shape such as square, rectangular, circular, oval, or the like. As best illustrated in FIG. 2, body portion 102 includes an arcuate, first end surface 104, at a distal or leading end 106, and a second end surface 108, having a corresponding arcuate profile to first end surface 104, opposite thereto at a proximal or trailing end 110. It is contemplated that first and second end surfaces 104, 108 may include other, non-corresponding combinations of profiles, such as arcuate and planar, planar and arcuate, and the like. Body portion 102 extends between first and second end surfaces 104, 108 to define respective top and bottom surfaces 112 and 114 (FIG. 3), respectively, as well as side surfaces 116, 118 (FIG. 2). As best illustrated in FIG. 4, top surface 112 approximates bottom surface 114 in a direction from side surface 118 towards side surface 116, although it is contemplated that top and bottom surfaces 112, 114 may be substantially planar relative to one another, approximate in a direction from side surface 116 towards side surface 118, approximate in a proximal direction, approximate in a distal direction, or any combination thereof. Additionally, top and bottom surfaces are illustrated as being substantially planar, although other configurations are also contemplated such as convex, concave, or the like. A distal portion of top and bottom surfaces 112, 114, respectively, approximate along a distal direction (FIG. 3) in order to facilitate insertion within the intervertebral space and enhance the atraumatic character of body portion 102. In this manner, the intersection of top and bottom surfaces 112, 114 with each of the first and second end surfaces 104, 108 and side surfaces 116, 118 may include a fillet or rounded configuration 120 to inhibit sharp edges from causing trauma to the surrounding tissue and/or vertebral bodies. Side surfaces 116, 118 are illustrated as being curved, forming rounded sides, however, it is contemplated that side surfaces 116, 118 may be planar. Although side surfaces 116, 118 are illustrated as curving in the same direction (i.e., side surface 116 is concave and side surface 118 is convex), it is contemplated that side surface 116 may curve in an opposite direction to that of side surface 118 (i.e., side surfaces 116, 118 are both convex), or side surfaces 116, 118 may curve toward each other (i.e., side surfaces 116, 118 are both concave).

Body portion 102 includes a through-bore or cavity 124 defined through side surface 116 although it is contemplated that through-bore 124 may be defined through side surface 118. As best illustrated in FIGS. 1 and 5, through-bore 124 defines a generally oval configuration through side surface 116 and increases in volume at an interior portion of body portion 102. The increase in volume permits through-bore 124 to receive a greater amount of biological material than is possible with a through-bore having planar side walls. In embodiments, the through-bore 124 may include any suitable cross-section when viewed along a plane extending vertically and/or horizontally through top and bottom surfaces 112, 114 and side surfaces 116, 118, such as spheroid, ovoid, ellipsoid, cuboid, pyramidal, cylindrical, trapezoidal, greek cross, clover, amorphous, or the like. In one non-limiting embodiment, through-bore 124 includes upper and lower undercuts 124 a and 124 b adjacent side surfaces 116, 118, respectively (FIG. 5), defining a generally greek cross profile. Although the wall thickness of each of top and bottom surfaces 112, 114 and side surface 118 are illustrated as having a substantially similar thickness, it is contemplated that top and bottom surfaces 112, 114 may include one wall thickness and side surface 118 may include a thinner or thicker wall thickness, or any combination thereof.

It is contemplated that through-bore 124 may receive allograft material, autograft material, calcium phosphate/bone marrow aspirate (BMA), autogenous material, synthetic materials comprised of a biocompatible, osteoconductive, osteoinductive, or osteogeneic material such as VITOSS® Synthetic Cancellous Bone Void Filler material, or any other suitable biological material known in the art. The increase in interior volume of through-bore 124 aids in retaining the biological material therein, reducing the possibility that the biological material may become detached from interbody spacer 100. Through-bore 124 includes a cross-sectional area or surface area that is greater than any orifice of the plurality of orifices detailed hereinbelow. In embodiments, through-bore 124 includes a surface area that is equal to or greater than 25% of the surface area of side surface 116.

With reference to FIG. 4, a portal 126 is defined through a proximal portion of opposed side wall 118 and extending into through-bore 124. In this manner, portal 126 and through-bore 124 are in open communication. Portal 126 allows bone ingrowth and in embodiments, is an attachment point for a suitable insertion instrument (not shown).

With reference to FIGS. 1 and 4, second end surface 108 includes a threaded aperture 122 defined therethrough and extending into through-bore 124, thereby placing threaded aperture and through-bore 124 in open communication. Threaded aperture 122 is configured to releasably engage a suitable insertion tool (not shown), such as that described in U.S. Patent Application Serial No. 2012/0158062, filed Oct. 11, 2011, the entire contents of which are hereby incorporated by reference herein.

Top and bottom surfaces 112, 114 of body portion 102 are configured to engage respective endplates of adjacent vertebral bodies. In this manner, a plurality of ridges or projections (i.e., teeth) 128 (FIG. 3) is disposed on each of top and surfaces 112, 114 to aid in securing interbody spacer 100 to each respective adjacent vertebral body and stability against fore and aft, oblique or side to side movement of interbody spacer 100 within the intervertebral space. Specifically, ridges 128 frictionally engage endplates of adjacent vertebral bodies and inhibit movement of the spinal implant 100 with respect to the adjacent vertebral bodies. In embodiments, a longitudinal groove 130 (FIG. 2) may be defined through the plurality of ridges 128 on a distal portion of top and bottom surfaces 112, 114.

Interbody spacer 100 is constructed of a biocompatible material, such as commercially pure titanium and includes a porosity capable of promoting bone ingrowth and fusion with a vertebral body. In this manner, top and bottom surfaces 112, 114 and opposed side surfaces 116, 118 have a surface roughness that can promote bone growth and fusion with interbody spacer 100. The surface roughness may be in a range of about 0.10-50 μm, and preferably in a range of about 3-4 μm. As can be appreciated, top and bottom surfaces 112, 114 and opposed side surfaces 116, 118 may include the same or different surface roughness's (i.e., the surface roughness of top surface 112 may be different than the surface roughness of bottom surface 114), or top and bottom surfaces 112, 114 and opposed side surfaces 116, 118 may not include a surface roughness; rather, top and bottom surfaces 112, 114 and opposed side surfaces 116, 118 may be smooth. In embodiments top and bottom surfaces 112, 114 and opposed side surfaces 116, 118 may include any combination of surface roughness or smooth surface. Additionally, a plurality of orifices 132 is defined therethrough configured to promote bone ingrowth. The plurality of orifices 132 is defined through each of top and bottom surfaces 112, 114 and side surfaces 116, 118 and may include any suitable cross-section such as circular, oval, square, hexagonal, rectangular, diamond, or the like. As can be appreciated, the plurality of orifices 132 defined through each of top and bottom surfaces 112, 114 and side surfaces 116, 118 may include the same cross-section or different cross-section, or combinations thereof (i.e., an intermixing of circular and diamond cross-sections on the same surface or different surfaces). In one non-limiting embodiment, the plurality of orifices 132 defined through top and bottom surfaces 112, 114 include a circular cross-section, whereas the plurality of orifices 132 defined through each of side surfaces 116, 118 include a generally diamond shaped cross-section.

The plurality of orifices 132 mimic bone growth along Haversian canals and lamellar structures of bone. In this manner, the plurality of orifices passes entirely through top and bottom surfaces 112, 114 and side surfaces 116, 118. Alternatively, the plurality of orifices 132 may be offset in relation to one another (FIG. 6). In this manner, an orifice 132 defined through bottom surface 114 will be offset from a corresponding orifice 132 defined through top surface 112. In embodiments, orifices 132 may be defined through top and bottom surfaces 112, 114 and side surfaces 116, 118 normal thereto or at angles relative thereto. In one non-limiting embodiment, orifices 132 are defined through top and bottom surfaces 112, 114 at angles incident relative to each other, thereby forming a chevron configuration. As can be appreciated, each of the orifices 132 formed through top and bottom surfaces 112, 114 and opposed side surfaces 116, 118, respectively, form a respective channel therebetween, thereby interconnecting an orifice formed through top surface 112 and an orifice formed through bottom surface 114, or an orifice formed through side surface 116 and an orifice formed through side surface 118. It is contemplated that the density of orifices 132 may be different on each of top and bottom surfaces 112, 114 and side surfaces 116, 118, respectively, or may increase or decrease in density at various location thereon. The plurality of orifices 132 includes diameters in a range of about 50-1000 μm, although diameters between 300-700 μm are preferable. As can be appreciated, for shapes other than circular, orifices 132 include a cross-sectional area in a range of about 0.0019 μm²-0.785 μm², although a cross-sectional area between 0.0707 μm²-0.385 μm² is preferable. As can be appreciated, the plurality of orifices 132 may include orifices 132 having varying sizes and shapes relative to each other. The plurality of orifices 132 reduce the density and stiffness of interbody spacer 100 to enable the application of bone putty or the like (e.g., bone morphogenetic proteins, etc.) to interbody spacer 100 to promote bone ingrowth and fusion of adjacent vertebral bodies secured to interbody spacer 100. Bone ingrowth and fusion strengthen interbody spacer 100, thereby reducing the probability that interbody spacer 100 would fracture and the likelihood that micromotion would occur would likewise be reduced. Alternatively, it is contemplated that interbody spacer 100 be constructed without orifices 132 defined therethrough, such that exterior surfaces of interbody spacer 100 have a smooth, uniform texture.

As can be appreciated, manufacturing interbody spacer 100 using standard machining methods (e.g., lathe, mill, EDM, etc.) could be difficult. In view of this, it is contemplated that in addition to manufacturing interbody spacer 100 using the aforementioned conventional means, interbody spacer 100 may be manufactured by means of additive manufacturing methods (e.g., SDM, SLPP, DMLS (i.e., EOS), SLS, SLM, SHS, EBM, VAT photopolymerisation, material jetting, binder jetting, or the like). In one non-limiting embodiment, interbody spacer 100 is may be manufactured using Selective Laser Powder Processing (SLPP). SLPP utilizes powdered metal and a laser which sinters or cures the metal in a selective fashion according to the design intent in thin layers. In embodiments, the layers have a thickness of about 250 μm. Interbody spacer 100 is built layer by layer to allow for more design options and features that would be difficult to be machined using conventional methods. Specifically, a first layer of powder is applied to a specialized build plate, at which point the laser cures portions of the powder according to the design intent. At this point, a second layer is applied to the build plate and the laser is again used to cure selective portions of this second layer. This process is repeated until interbody spacer 100 is fully formed. Once interbody spacer 100 is fully formed, uncured powder is removed using compressed air or other similar means. Next, post machining is performed on interbody spacer 100 to remove any burrs or similar imperfections embedded within interbody spacer 100 during the additive manufacturing process. In embodiments, the burrs are removed by means of buffer wheels, clippers, files, or the like. Once de-burred, interbody spacer 100 is heat treated, and thereafter, media blasted using aluminum oxide. Thereafter, interbody spacer 100 is immersed in a hydrofluoric bath to strip the aluminum oxide therefrom. Finally, interbody spacer 100 is inspected by quality control personnel (or using automated means), cleaned via ultrasonic cleaning, dried, and packaged. It is contemplated that the design of interbody spacer 100 may be customized for each specific patient using SLPP. For a detailed description of exemplary manufacturing methods, reference may be made to U.S. Pat. No. 8,590,157, issued on Nov. 26, 2013 to Kruth et al., the entire contents of which are hereby incorporated by reference herein.

Interbody spacer 100 may be constructed from commercially pure titanium, titanium alloy, cobalt-chrome, ceramic, Polyetheretherketone (PEEK), or any other suitable biocompatible material. In embodiments, interbody spacer 100 may be manufactured using a three-dimensional printer utilizing a biocompatible polymer.

With reference to FIGS. 1-5, in use, an intervertebral space is first prepared, e.g., damaged or diseased tissue is removed. Thereafter, an appropriately sized interbody spacer 100 is selected based on the patient's spinal characteristics and the desired amount of lordosis. Next, the interior space of through-bore 124 of body portion 102 may be packed with bone in-growth material, drugs, or other suitable biological materials or compounds. Examples of such materials are allograft material, or synthetic materials comprised of a biocompatible, osteoconductive, osteoinductive, or osteogeneic material such as VITOSS® Synthetic Cancellous Bone Void Filler material. Next, a suitable insertion instrument (not shown) is threaded into threaded aperture 122 of body portion 102 until interbody spacer 100 is securely affixed to the insertion instrument. At this point, interbody spacer 100 is advanced within an incision within the patient, and thereafter, into the previously prepared intervertebral space of the patient's spine. Once interbody spacer 100 is placed within the intervertebral space such that interbody spacer 100 rests on the distal apophyseal ring of the vertebral body, the tool (not shown) is released from threaded aperture 122, and thereafter, removed from the incision within the patient. Residing on the apophyseal ring facilitates fusion between the intervertebral plates and interbody spacer 100, as interbody spacer 100 is less likely to experience subsidence into the end plates.

This process may be repeated as many times as the procedure requires, whether it be for the same interbody spacer 100 or for a plurality of interbody spacers 100 as required by the procedure being performed.

It is envisioned that the manufacturing processes and orifice designs detailed above may be utilized to form various other medical devices known in the art. In this manner, the additive manufacturing process detailed above may be employed to form corpectomy devices, fixed spinal implants, expandable spinal implants, bone screws, cervical implants, and the like. Similarly, the orifice designs detailed above may be formed in any of the beforementioned medical devices that would benefit from an increased ability to fuse with bone. Examples of such devices may be found in the following commonly owned references: U.S. Pat. No. 8,585,761 to Theofilos, U.S. Pat. No. 8,673,011 to Theofilos et al., U.S. application Ser. No. 14/936,911 to Sutterlin et al., U.S. Pat. No. 8,801,791 to Soo et al., U.S. Pat. No. 8,439,977 to Kostuik et al., U.S. Patent Application Publication No. 2010/0100131 to Wallenstein, U.S. Patent Application Publication No. 2012/0179261 to Soo, U.S. Pat. No. 8,449,585 to Wallenstein et al., U.S. Pat. No. 8,814,919 to Barrus et al., U.S. Pat. No. 5,733,286 to Errico et al., and U.S. Patent Application Publication No. 2013/0046345 to Jones et al.

It will be understood that various modifications may be made to the embodiments of the presently disclosed interbody spacer. Therefore, the above description should not be construed as limiting, but merely as exemplifications of embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the present disclosure. 

What is claimed is:
 1. An interbody spacer, comprising: a body portion including a distal end portion, a proximal end portion, first and second side surfaces that extend between the distal and proximal end portions, and top and bottom surfaces configured and adapted to engage vertebral bodies, the top and bottom surfaces defining a vertical axis therethrough, wherein the body portion includes a cavity defined through the first side surface, the cavity increasing in volume at an interior portion of the body portion and defining a sidewall having an arcuate profile extending between the top and bottom surfaces and along the vertical axis, wherein the cavity includes undercuts defined therein, the undercuts defining a concave sidewall forming a portion of the sidewall of the cavity; first orifices defined through the top surface; and second orifices defined through the bottom surface, one of the first orifices having a cross-sectional configuration different from that of one of the second orifices.
 2. The interbody spacer of claim 1, wherein the cavity includes undercuts defined therein.
 3. The interbody spacer of claim 1, wherein an interior dimension of the cavity increases in a direction towards each respective top and bottom surface.
 4. The interbody spacer of claim 1, wherein the cavity includes a greek cross cross-sectional configuration.
 5. The interbody spacer of claim 1, wherein each of the first and second side surfaces includes an arcuate configuration.
 6. The interbody spacer of claim 1, wherein the body portion defines a kidney shaped configuration.
 7. The interbody spacer of claim 1, wherein one of the first orifices is offset from one of the second orifices.
 8. The interbody spacer of claim 1, wherein one of the first orifices includes a circular cross-section.
 9. The interbody spacer of claim 1, wherein one of the second orifices includes a diamond-shaped cross-section.
 10. The interbody spacer of claim 1, wherein one of the first orifices includes a circular cross-section and one of the second orifices includes a diamond-shaped cross-section.
 11. The interbody spacer of claim 1, wherein the interbody spacer is formed using an additive manufacturing process.
 12. The interbody spacer of claim 1, wherein a portal is defined through the second side surface.
 13. The interbody spacer of claim 1, wherein a threaded aperture is defined through the proximal end portion, the threaded aperture configured to threadably engage an insertion tool.
 14. The interbody spacer of claim 1, wherein a plurality of ridges is disposed on each of the top and bottom surfaces.
 15. The interbody spacer of claim 14, wherein a longitudinal groove is defined through a portion of a ridge of the plurality of ridges.
 16. A method of performing spinal surgery, comprising: preparing an intervertebral space between first and second vertebral bodies; and advancing an interbody spacer into the intervertebral space, the interbody spacer including: a body portion including a distal end portion, a proximal end portion, first and second side surfaces that extend between the distal end proximal end portions, and top and bottom surfaces configured and adapted to engage vertebral bodies, the top and bottom surfaces defining a vertical axis therethrough, wherein the body portion includes a cavity defined through the first side surface, the cavity increasing in volume at an interior portion of the body portion and defining a sidewall having an arcuate profile extending between the top and bottom surfaces and along the vertical axis, wherein the cavity includes undercuts defined therein, the undercuts defining a concave sidewall forming a portion of the sidewall of the cavity; first orifices defined through the top surface; and second orifices defined through the bottom surface, one of the first orifices having a cross-sectional configuration different from that of one of the second orifices.
 17. The method according to claim 16, wherein advancing the interbody spacer includes the interbody spacer having a cavity that includes undercuts defined therein.
 18. The method according to claim 16, further including packing the cavity with bone in-growth material.
 19. The method according to claim 16, further including packing the cavity with drugs. 